A number of different automated clinical chemical analyzers are known in the art. Such analyzers range from simple, largely manually-operated instruments to highly complex, nearly fully automated instruments. One class of clinical chemical analyzer which has proved very successful is a class of clinical chemical analyzers which employ a nephelometer and/or a turbidimeter as the operative analytic instrument. Such chemical analyzers have been found to be highly efficient in analyzing a wide variety of liquid chemical solutions, especially liquid chemical solutions of interest to medical hospital facilities and medical research laboratories.
In both nephelometry and turbidimetry, a light source is projected through a liquid sample retained within a transparent sample container. Particulate matter or other sources of turbidity within the liquid sample cause some of the incident light to scatter. The quantity of such scattered light can be closely correlated to at least one parameter of the sample. Generally, nephelometry uses a light source having a relatively short wave length (e.g., 500 nm-800 nm) and is effective in detecting very small particulate matter. Turbidimetry, on the other hand, generally uses light sources having longer wave lengths (e.g., 800 nm-1100 nm) and is effective in detecting particulate matter of larger size. The theory of nephelometry and turbidimetry as used in automated chemical analyzers is discussed in detail in U.S. Pat. No. 5,296,195, which is incorporated herein by reference.
As sophisticated and efficient as modern automated chemical analyzers using nephelometry and turbidimetry combinations have become today, several problems continue to exist. A first problem is control of the laser commonly used in such machines. Typically, such laser produces a light beam which is highly polarized, having a P-wave component and an S-wave component. In most cases, scattering from only one of these polarized components is measured in the analysis machine. Unfortunately, prior art machines have attempted to regulate the power output from the laser by controlling the total energy from the laser beam, including both polarized components. Attempting to control the laser in this way has proved unsatisfactory because a variation in the relative percentage of the two polarized components within the total beam is not perceived by the controlling mechanism. Thus, the light energy of the polarized portion actually used in the analysis machine may vary from test to test. This adversely affects the reliability and accuracy of the analytical process.
A second problem with such automated analyzing machines of the prior art arises because some of the polarized light from the laser is commonly reflected off of the turbidimeter light receptor focusing lens back into the analysis container. Some of this polarized light is scattered by the sample in the analysis container and is measured by the nephelometer light receptor. This may result in the nephelometer receptor registering a falsely high reading. This phenomenon also adversely affects accuracy and reliability of the analytical process.
Accordingly, there is a need for a nephelometer analyzing system and a nephelometer/turbidimeter combination which is more accurate and more reliable than systems of the prior art.